X-ray sources in NSVS

Tim McKay

University of Michigan

04/03/04

The ROTSE-I Instrument

• Optics: four Canon f/1.8 200mm lenses

• Cameras: 4 20482 CCDs (14.4” pixels)

• 16°x16° field of view• Rapid slewing mount• Five Linux control

computers• A lot of software

(Kehoe + Marshall)

ROTSE-I Operations

• Completely automated, unattended, operation (8 Gbytes/night)

• Usually, an all-sky patrol instrument– 4 patrols (2 pairs) of the entire sky nightly, 80s

exposures– Paired images for background rejection– Unfiltered observations

• All instantly interruptable by GCN for triggered responses: GRBs

• Operated March 1998-Dec 2001

Inside the toaster…..

The toaster….

ROTSE Sky Patrols: keeping a nightly watchLarge field of view allows full sky coverage (4) in 206 fieldsEverything with elevation >20° observed every night>90 fields and 20,000 square degrees a night

Everything to-30 regularlypatrolled

Initial ROTSE-I Patrol Analysis•Test analysis of 9 (out of 160) fields: 2000 square degrees

•5% of the entire sky, 1/17th of available ROTSE-I data•Four months of data (March to June 1999, 40-120

epochs)

Note wide range of latitudes

RSV1 fields

Northern Sky Variability Survey

• ROTSE-I data from April 1999-March 2000

• Covers ~33,000 square degrees: 80% of the sky, best for 50%...

• 184,000 CCD images• 257/365 nights

• Ntotal = 14.5 million

• 3.3 billion light curve points

• Unfiltered CCD data• Calibration from 1500

Tycho stars / frame

Number density Photometric scatter

Number of light curve points Number of ‘good’ points

Variability analysis

• A first quick-look based on a few days work….

• Variability selection with modified Welch-Stetson algorithm

• Require 20 pairs of observations…

Var

iabi

lity

Inde

x

Magnitude: roughly V…

All variables

Long Period Variables

Short Period Variables

Auxiliary data

• Comparison to other all-sky surveys is particularly enlightening

• Two-Micron All Sky Survey provides J, H, and K data for all these objects

• Roughly the same epoch…

• ROSAT All-Sky Survey provides possible x-ray counterparts

• IRAS provides far-IR counterparts to many

• Other possibilities include FIRST, NVSS, SDSS, Tycho, USNOB…..

These figures show the J-H vs. H-K color-color plots for RVS1 variables in four classes. Note that the color ranges confirm the classifications well. The splitting in the intermediate period population suggests that these colors can be used for further classification.

2MASS period-color relations for Contact Binaries and Delta Scuti stars. These relatively tight relations suggest that decent distance estimates can be obtained for these objects.

Matching to RASS

• RASS BSC and FSC include 124,000 objects

• RASS positions accurate to between 20 and 40”

• ROTSE-I positions to <5”

• Cross-match by position

• Compare to matches with randomized positions

• Check that matches are drawn from particular subsets of variable types

1424

111

RASS matching to 44” square….

Matches to real ROTSE positions

Matches to randomized ROTSE positions

RASS CPS distributions for all, and for those which match ROTSE-I variables…

Some goals

• Classify the NSVS variables

• Explore 2MASS information for classification and distance estimation

• Estimate x-ray flux from contact systems

• Work on contact binary space density

• Explore the long period variables, especially with 2MASS and IRAS infrared information